Process of and product for photographic etching



Patented Mar. 17, 1931 tov Barron or PENNSYLVANIA nRooninef-nA-vrs; on crnornnnmr; 01110; nssrenomBar- ESH?assremliliwa T0 EYs'roNEwArorr oAsE eo'nrcirm'rron, or VRIVERSIDIEQ'NEW,JERSEY, 1.5?00310:

mmoessoeAnnmower:roa-rireweesarmdM mes No Drawing, Originalapplicaticn mammogr m 1e, 1.926, Serial'N 0-e-155,3 7 widened this. pp et tion filed-Novembera, 1928.; seriarnm 318,312

" invention relates to n'ovelimprove ments in the art of photography, and 'itha's particularly to do witha photographic film which has special 'advantageswhen used in the process, of etching. The, invent on also pertainsflt'o,anovel process of preparing the filin and tdthe-pro'cess of using and treating the fihnwhen employed, for instance, in etching ancl similarwo'rk.

filed December 16,1926, Serial Number 155,-

336, directed to improvements in the detail of that process described by E. Valenta of Vienna, Austria, in Photographische Korrespondenz, 1910 at pages 238-40, where Valenta makes a light sensitive resist for photo etching by reacting upon asphalt with sulfur chloride, Valenta adding the sulfur chloride solution very slowly, while my improvements call for the immediate addition of the entire quantity necessary for the reaction, which is approximately eight per cent of the weight of the asphalt. Also, in my copending application, I have further'improved the quality of the resist by washing it in film form with ether after its application to the surface to be etched. I have now found that this step may be advantageously carried out on the basic substance, thereby shortening e the detail of operation by removing the ether [soluble portion from the resist en masse.

This process may be carried out in detail as follows: To grams of any ordinary asphalt, dissolved in 150 cc. carbon bisulphide, 2 grams of sulfur chloride dissolved in 8 cc. carbon bisulphide is added all at once, and the reaction allowed to proceed at the boiling point of the solvent until it has gone to practical completion. The balance of the carbon bisulphide which can be removed at water bath temperature isthen driven off and'there is then added 500 cc. of ethyl ether and the mass thoroughly shaken. There dissolves in asphalticmaterial, and this solvent action h s v the ether the more soluble portion bf th a of the etheris selective so far-as"lightssensitiw ity' concerned, themate'rial which goes into solution *beii'rg the least light sensitive. The ether is W. decanted,fromjthe-blaek, semi solid residue andethe fin a'l portion of ether driven 0E ohthejwaterbathi The residu'e is then dissolved :iIi cc; of benzo'l {a nd this solution filtered" from a sniall-jportion of insoluble' matter. This benzol solution now constitutes the resist; which is ready for ap plication to thesurfaeetobe etched; Designs borne by a glassjscreen; or otherwise, are interposed between an arc fitted with a suitable icondenser'andthe surface bearing "the resist,

and the designs; are --projected on the resist, the portions of the resist n ot renderedinsohtbl'e by the action of light are} removed'by a solventincludingturpentineg and the etching maybe-accoinplished =by=known processes:

Fromexpernne'nts, I have found-thatvalemme; process is? somewhat diff cult to use practically on account ofun uniform result s,

thedetails which Thrive addedi so far perfect "theva lentaprocess that e'nti rely 'unifdrm iresults are;obtainedusing practioallyr-any kind of? soft commercial; asphalt, such as Trinidad or Mex-ic'an asphaltr hat I believe to be novel improvements on Valentas process'% are thesteps in the process det'a'ilof addingthe carboff bisulpliide 'selution of sulfur chloride tothe' asplialt al-l a-t o11ce-,isince under these conditions the*reaetionseems to'take1an en:- tii'ely different ndanore' highly de'sirabl'e course than when addedfias di 'recteclaby .Valenta, and" also the step of removingthe ether soluble 11 portions of the resulting reaction product of the mas as descri-be d inste ad of than asphalt, for if the prbcessibe.carried out exactly as: described, but using:- pineresin in {pla e of asphalt, a resist!suitable-"for photo etching? is ebt' str'ct the app capable of removing the undesirable portion of the reaction mass I regard as falling within the scope of this invention.

. Ordinary asphalt yieldscolloidal solutions, as do also its reaction products with sulfur chloride, and the sulfur chloride apparently both chlorinates and sulfurizes the various asphaltic ingredients, products which are not only light sensitive, but others which act as catalysts or accelerators for the light sensitive portion. The ultimate film, therefore,

' consists of a hydrophobic colloid including sensitizers or catalysts. The sensitivity is still further increased, as directed by Valenta, by the addition of 2% of oil of lavender, this oil being high in aldehydes which apparently act in a catalytic manner as Well as by direct condensation for increasing the light sensitivity of the film. I

It is evident from the above that my resist consists of hydrophobic colloids includingcatalysts and sensitizers therefor, and the process detail as above described has so far increased the value of asphalt as a photographic resist that'it is thoroughly practical for use in plant operations, beingstable for at least sixweeks without deterioration and capable of being rendered insoluble by light exposure with ordinary arc projection machines in less than one minute, and I have obtained good pictures in seconds which have withstood the action of an electrolyte etching bath for minutes. These results are a great improvement over the results obtained by other researchers.

It is to be understood that the foregoing description of the improved resist and the process ofuse thereof may be varied to some extent, but such variations and changes as may be desired are considered as being within the scope of the invention as would be permitted by the broad interpretation of the following claims. a

What I claim is:

r 1. In the process of etching, the stepscomprising forming a light sensitive hydrophobic colloid by reacting a carbon bisulphide solution of an asphalt base material with a carbon bisulphide solution of sulphur chloride en masse, and removing the non-reacted lightinsensitive portions, placing a film of the light-sensitive residue on an object to be etched, projecting a design onto said film, developing, and etching.

2. In the process of etching, the steps of placing on an object to be etched a film of a light-sensitive hydrophobic colloid, pro- 7 jecting a design on said film, developing, and

etching, said hydrophobic colloid being the light-sensitive reaction product of the bulk treatment of a carbon bisulphide solution of asphalt-like materials with a carbon bisul phide solution of sulphur chloride which product has been treated with ether to remove light-insensitive reaction products.

' tions of asphalt and sulphur chloride which has been treated with ether to remove unreacted light-insensitive portions.

4:. A photographic print comprising the photo-reaction products of a sensitized lightsensitive hydrophobic colloid resulting from the bulk treatment of a carbon bisulphide solution of a colloid base material with a carbon bisulphide solution of sulphur chloride en masse, which colloid has been treated with ether to remove unreacted light-insensitive portions.

5. A photographic print comprising the photo-reaction products of the sensitized light-sensitivereaction products of the treat ment, en masse, of asphalt with sulphur chloride, the asphalt and the sulphur chloride being severally dissolved in carbon bisulphide, and the reactionproducts Washed with ether to remove unreacted light-insensitive portions.

ALEX BROOKING DAVIS. 

